Diesel Exhaust System Reversible Particulate Filter

ABSTRACT

The invention concerns a diesel particulate filter in an exhaust system of a vehicle having a diesel engine. The particulate filter may have soot burned out via a regeneration process, and may be serviced for ash buildup by selectively reversing the diesel particulate filter, or its brick, in the exhaust system.

BACKGROUND OF INVENTION

The present invention relates generally to an exhaust system in avehicle having a diesel engine.

Recent emissions regulations for vehicles employing diesel engines limitthe amount of soot that the vehicles may emit. The soot is produced as aby-product of the combustion of the diesel fuel and is emitted with thevehicle exhaust. Diesel particulate filters (also called traps) added tothe exhaust system limit the soot emissions sufficiently to meet theregulations.

Diesel particulate filters work by collecting the soot while allowingthe exhaust gases to pass through. As the vehicle operates, then, thesoot builds up in the filter. This soot needs to be periodicallyeliminated from the filter in order to assure that the filter does notbecome clogged. A clogged filter can potentially cause damage to itselfor the engine. The soot that builds up in the filter can be removedthrough a process called regeneration. Regeneration is performed byheating the diesel particulate filter to a temperature where the sootwill burn away, thus cleaning out the filter.

Unfortunately, ash also tends to collect in the diesel particulatefilter. Ash is different than soot. During engine operation, thelubrication oil used in diesel engines works its way into the enginecylinders. This lubrication oil includes additives. While the oil isburned during combustion events, the additives exit the engine cylindersand flow into the exhaust system as ash—along with the soot. A dieseloxidation catalyst, which is typically employed in a diesel exhaustassembly, is a flow through catalyst and so the ash and soot do notbuild up in it. But the ash, along with the soot, do collect in thehoneycomb structure of the diesel particulate filter. The soot can beburned away through the regeneration process, as discussed above, butthe ash cannot be burned away under this process. After many miles ofdriving the vehicle, then, the ash buildup in the diesel particulatefilter will make the backpressure in the exhaust system too high.

The diesel particulate filter must be repaired (if serviceable) orreplaced when it is no longer functioning properly. The dieselparticulate filter is expensive to replace, and so this is undesirableif it is possible to service the filter. But servicing by disassemblinga diesel particulate filter assembly and cleaning the ash from the brick(the honeycomb structure) is also a time-consuming and costly solutionthat is less than desirable.

It is desirable, therefore, to provide an exhaust system employing adiesel particulate filter with a means for continuing the use of thediesel engine exhaust system for as many miles of vehicle use aspossible, while minimizing the cost of replacement or servicing of thefilter due to ash buildup.

SUMMARY OF INVENTION

An embodiment contemplates an exhaust system for a vehicle having adiesel engine. The exhaust system may comprise a diesel particulatefilter having a first end and an opposed second end, a first pipe,located upstream of the diesel particulate filter, for directing exhaustgases into the diesel particulate filter, and a second pipe, locateddownstream of the diesel particulate filter, for receiving exhaust gasesfrom the diesel particulate filter. The exhaust system may also comprisea first mounting flange mounted on the first end of the dieselparticulate filter, mountable on either of the first pipe and the secondpipe, and mounted on one of the first pipe and the second pipe, and asecond mounting flange mounted on the second end of the dieselparticulate filter, mountable on either of the first pipe and the secondpipe, and mounted on the other of the first pipe and the second pipe.

An embodiment contemplates a method of monitoring and servicing a dieselparticulate filter that may become loaded with ash, in an exhaust systemof a vehicle having a diesel engine, the method comprising the steps of:monitoring at least one parameter indicative of a buildup of the ash inthe diesel particulate filter; determining from the at least oneparameter if action is required due to the ash buildup in the dieselparticulate filter; indicating that diesel particulate filter servicingis needed when it is determined that action is required; and reversing adirection of exhaust flow through a brick in the diesel particulatefilter when servicing is needed and if reversal is desirable.

An embodiment contemplates a method of regenerating and servicing adiesel particulate filter in an exhaust system of a vehicle having adiesel engine, the method comprising the steps of: (a) operating thediesel engine and exhaust system in a normal operating mode; (b)monitoring at least one soot parameter indicative of soot buildup in thediesel particulate filter while operating in the normal operating mode;(c) monitoring at least one ash parameter indicative of a buildup of theash in the diesel particulate filter; (d) determining from the at leastone soot parameter when the diesel particulate filter needsregenerating; (e) operating the vehicle in a regeneration mode, if it isdetermined in step (d) that the diesel particulate filter needsregenerating; (f) determining from the at least one ash parameter ifaction is required due to the ash buildup in the diesel particulatefilter; and (g) reversing a direction of exhaust flow through a brick inthe diesel particulate filter when step (f) determines that action isrequired.

An advantage of an embodiment is that the useful life of a dieselparticulate filter is significantly increased.

An advantage of an embodiment is that the cost to extend the useful lifeof the diesel particulate filter is minimized.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a vehicle with a diesel engine,and a portion of an exhaust system for the vehicle.

FIG. 2 is a side view of a diesel particulate filter.

FIG. 3 is a section view taken along line 3-3 in FIG. 2.

FIG. 4 is a flow chart illustrating the diesel particulate filtermonitoring and reversal process.

FIG. 5 is a flow chart similar to FIG. 4, but illustrating analternative embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a vehicle 20 having an engine compartment 22, with adiesel engine 24 mounted therein. The diesel engine 24 drives atransmission 26, which, in turn, drives a vehicle driveline 28, and,ultimately, vehicle wheels 30. A controller 32 operatively engages thediesel engine 24 and transmission 26. The controller 32 may be made upof one or more discrete controllers, and may be formed from variouscombinations of software and hardware, as is known to those skilled inthe art.

An exhaust system 34 receives exhaust gases 36 from the diesel engine24, treats the exhaust gases 36, and directs them into the atmosphereaway from the vehicle 20. More specifically, an exhaust pipe 42 connectsat an upstream end to conventional exhaust system hardware (not shown),such as, for example, a turbocharger (not shown), that receives exhaustfrom exhaust manifolds (not shown) on the engine 24. The exhaust pipe 42directs the exhaust gases 36 into a diesel oxidation converter 44 (alsoknown as a diesel oxidation catalyst). The diesel oxidation converter 26treats the exhaust gases 36 in order to reduce the amounts of certainconstituents that will be emitted into the atmosphere. Such constituentsmay be, for example, carbon monoxide (CO) and unburned hydrocarbons(HC). The vehicle and its components discussed above are known to thoseskilled in the art and so will not be discussed or shown in more detailherein.

A first intermediate pipe 38 connects to the downstream end of thediesel oxidation converter 44 and directs the exhaust gases 36 into adiesel particulate filter 50 (also called a diesel particulate trap).The diesel particulate filter 50 is basically a filter for collecting(i.e., trapping) soot (also called diesel particulate matter) from theexhaust in order to minimize the amount of soot in the exhaust gases 36.Downstream of the diesel particulate filter 50 is a second intermediatepipe 40. The second intermediate pipe 40 directs the exhaust gases 36into a muffler 46. The muffler directs the exhaust flow into a tailpipe48, which extends to an open downstream end where the exhaust gases 36are emitted into the atmosphere away from the vehicle 20.

The exhaust system 34 may also include an upstream pressure sensor 80,which is mounted just prior to exhaust gas entry into the dieselparticulate filter 50 in order to measure the pressure in the exhaustgas stream just prior to entry into the filter 50. A downstream pressuresensor 82 may be mounted in the exhaust system 34 just after the exhaustexit from the diesel particulate filter 50 in order to measure thepressure in the exhaust gas stream after exit from the filter 50. Boththe upstream and downstream pressure sensors 80, 82 are in communicationwith the controller 32. The controller 32 may also be in communicationwith various components of the diesel engine 24 and transmission 26, asis known to those skilled in the art. The controller 32 may also beconnected to an indicator light 33 mounted, for example, on aninstrument panel (not shown).

The diesel particulate filter 50 will now be discussed in more detailwith reference to FIGS. 1-3. The particulate filter 50 includes ahousing (also called a can) 52, which has a generally cylindrical shell54 mounted between an inlet cone 56 on an upstream end and an outletcone 58 on a downstream end. Brick support material 60 is mounted aroundthe inside of the shell 54 and supports a brick 62. The brick 62 may bea wall-flow honeycomb structure, with an upstream end 64 facing an inletchannel 66 defined by the inlet cone 56, and a downstream end 68 facingan outlet channel 70 defined by the outlet cone 58. A support ring 72may also mount around a portion of the brick 62. The diesel particulatefilter 50 may be catalyzed or uncatalyzed. If catalyzed, then a catalystwash coat should be applied evenly to both the inlet and outletchannels.

The diesel particulate filter 50 includes a first mounting flange 74 onan upstream end and a second mounting flange 76 on a downstream end.Both of the mounting flanges 74, 76 can be attached to either of thefirst and second intermediate pipes 38, 40. These flanges 74, 76 arealso preferably of the type that allow for removal and reinstallation ofthe diesel particulate filter 50. The mounting flanges 74, 76 may be,for example, a V-bend type of flange. This is just one example, sincethere are many types of mounting flanges 74, 76 that can be employed toallow for removal, reversal and reinstallation of the diesel particulatefilter 50. Moreover, the term mounting flange as used herein is to beinterpreted broadly to include many known exhaust pipe joints that canbe used to mount the diesel particulate filter 50.

FIG. 4 illustrates a method for prolonging the useful life of the dieselparticulate filter 50, as illustrated in the exhaust system 34 of FIGS.1-3. As the diesel engine 24 operates, the exhaust gases 36 flow fromthe engine 24, through the diesel oxidation converter 44, the dieselparticulate filter 50, the muffler 46, and through the tailpipe 48 intothe atmosphere. As exhaust gases flow through the exhaust system 34,soot and ash are collected in the brick 62 of the diesel particulatefilter 50, and build up over time. A determination, then, needs to bemade as to when the soot and when the ash have built up to a level whereaction needs to be taken. Accordingly, one or more parameters fordetermining the amount of soot buildup are monitored, step 100, and oneor more parameters for determining the amount of ash buildup aremonitored, step 102.

A comparison is made between the soot buildup parameter(s) andpredetermined threshold(s) to determine if soot regeneration isrequired, step 104. If not, then a comparison is made between the ashbuildup parameter(s) and predetermined threshold(s) to determine ifaction needs to be taken due to ash buildup, step 108. If not, then themonitoring continues.

At some point, a determination is made (step 104) that the soot needs tobe burned off (i.e., the filter regenerated) in order to avoid cloggingthe diesel particulate filter 50. The determination of when theregeneration mode will be initiated can be based on one or more ofseveral factors (parameters). For example, the controller 32 may keeptrack of engine run time, vehicle mileage or fuel consumption since thelast regeneration process occurred, and initiate the regenerationprocess after a predetermined amount of engine run time, vehicle mileageor fuel consumption, as the case may be. For another example, thecontroller 32 may determine the pressure drop across the particulatefilter 50 by calculating the difference in measured pressure between theupstream pressure sensor 80 and the downstream pressure sensor 82, withthe regeneration process initiated when a predetermined pressuredifference across the particulate filter 50 is reached. Or, thecontroller 32 may employ a soot regeneration algorithm that estimates anamount of soot buildup based upon some combination of two or more of theprevious listed factors, or other factors.

When the determination is made that regeneration of the particulatefilter 50 is needed, the controller 32 begins the regeneration process,step 106. The controller 32 will cause the regeneration process to occurby various known means. The particular actions taken by the controller32 may depend upon the engine and vehicle operating conditions as wellas the ambient conditions. The temperature of the diesel particulatefilter 50 is raised sufficiently to cause soot to burn off. Thecontroller 32 continues with the process until the desired amount ofregeneration is achieved. This may be based, for example, on apredetermined pressure drop across the particulate filter 50 beingachieved, a predetermined length of regeneration time, or a sootregeneration algorithm that estimates the amount of soot burn-offachieved.

At some point, a determination is made (step 108) that the ash buildupis sufficient that action needs to be taken. One will note that it iscontemplated that the regeneration for soot occurs far more frequentlythan any action needed to account for ash buildup. For example, sootregeneration may happen as often as every fuel tank fill, while actiontake for ash buildup may not be required until around 200,000 kilometersof vehicle travel. The determination that action is required for ashbuildup may be based on, for example, measuring the pressure drop acrossthe diesel particulate filter 50—in particular if the pressure drop isabove a predetermined threshold even after soot regeneration. Examplesof other possible determining factors may be reaching a certain mileagewith the diesel particulate filter in the same orientation, or anincrease in fuel consumption by the diesel engine 24. Or, a combinationof two or more of these factors, or others, may be employed to make thisdetermination. The particular factors and thresholds used may dependupon the particular vehicle, engine and exhaust system to which thismethod is applied.

If the ash buildup requires action, then an indication is provided thatdiesel particulate filter reversal or replacement is needed, step 110.This indication may be, for example, the light 33 that illuminates on aninstrument panel (not shown), or a wireless data transmission to acomputer network (not shown) that will email an operator of this need.Of course, other types of indicators that will notify a vehicle operatorof the need to take action for ash buildup can also be employed instead,if so desired.

With the wall-flow honeycomb structure of the brick 62 in the filter 50,the ash that builds up will tend to build up near the upstream end 64 ofthe brick 62. Thus, turning the entire filter 50 (or just the brick 62)around will locate the part of the brick 62 with the most ash buildup(the end that was originally upstream) on the downstream end facing theoutlet channel 70. This will allow the built-up ash to be blown out inthe exhaust stream 36 as it passes from the brick 62 into the outletchannel 70. As noted above, the first and second mounting flanges 74, 76can each connect to either the first intermediate pipe 38 or the secondintermediate pipe 40, and allow for removal and reinstallation of thediesel particulate filter 50.

Accordingly, a determination is made as to whether reversal isdesirable, step 112. If it is not desirable to reverse the filter 50,then the diesel particulate filter 50 is replaced, step 116. If it isdesirable to reverse the filer 50, then it is removed from the exhaustsystem 34, reversed (i.e., rotated 180 degrees from its originalorientation), and then reinstalled in the exhaust system 34, step 114.The controller 32 can then be reset and the process starts over again.

Reasons to replace instead of reverse the filter 50 may be, for example,that it has already been reversed previously at least once and, for thisparticular vehicle, engine and filter combination, it is not desirableto reverse it an additional time. Another reason may be that, forexample, this particular filter 50 is clogged, rather than just fullyloaded with ash. A fully-loaded filter 50 signifies that it is time totake some action relative to the ash buildup—the engine and exhaustsystem will still function though somewhat less efficiently. Cloggedsignifies that the filter 50 is no longer functioning—the engine andexhaust system will run very poorly or maybe not at all for thiscondition. Of course, where possible, the filter 50 is preferablyreversed since this will generally cost significantly less thanreplacement.

FIG. 5 illustrates an alternative method to that in FIG. 4. In thisembodiment, steps that are similar to those in FIG. 4 will be similarlydesignated, but using 200-series numbers. This method essentiallyseparates the process for dealing with ash buildup from the process fordealing with soot buildup. Such a separate process may be desirablesince soot regeneration occurs relatively frequently, while ash buildupis something that may only need attention once or twice during theentire life of the vehicle.

The parameter(s) for ash buildup are monitored, step 202. A comparisonis made between the ash buildup parameter(s) and predeterminedthreshold(s) to determine if action needs to be taken due to ashbuildup, step 208. If not, then the monitoring continues. If the ashbuildup requires action, then an indication is provided that dieselparticulate filter reversal or replacement is needed, step 210. Adetermination is made as to whether reversal is desirable, step 212. Ifit is not desirable to reverse the filter 50, then the dieselparticulate filter 50 is replaced, step 216. If it is desirable toreverse the filer 50, then it is removed from the exhaust system 34,reversed (i.e., rotated 180 degrees from its original orientation), andthen reinstalled in the exhaust system 34, step 214.

For the processes described above, there may be alternative ways toaccomplish some of the steps. For example, this process comprehends thetechnique of servicing a diesel particulate filter 50 that is loadedwith ash by reversing it, but reinstalling it on another vehicle. Asanother alternative, this process can include ash removal beforereinstallation. As yet another alternative, this process can include thediesel particulate filter 50 being removed, the housing 52 being opened,the brick 62 removed and reinstalled in the housing 52 in the reversedirection, and then reinstalling the housing 52 in the exhaust system 34in the same direction. Or, as a further alternative, the housing 52 mayremain attached to the exhaust system 34 while being opened, the brick62 removed, reversed and reinserted, and the housing 52 closed again.

While certain embodiments of the present invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention as defined by the following claims.

1. An exhaust system for a vehicle having a diesel engine comprising: adiesel particulate filter having a first end and an opposed second end;a first pipe, located upstream of the diesel particulate filter, fordirecting exhaust gases into the diesel particulate filter; a secondpipe, located downstream of the diesel particulate filter, for receivingexhaust gases from the diesel particulate filter; a first mountingflange mounted on the first end of the diesel particulate filter,mountable on either of the first pipe and the second pipe, and mountedon one of the first pipe and the second pipe; and a second mountingflange mounted on the second end of the diesel particulate filter,mountable on either of the first pipe and the second pipe, and mountedon the other of the first pipe and the second pipe.
 2. The exhaustsystem of claim 1 wherein the diesel particulate filter includes a brickthat has a wall-flow honeycomb structure.
 3. The exhaust system of claim1 including a diesel oxidation converter connected to an upstream end ofthe first pipe.
 4. The exhaust system of claim 1 including a mufflerconnected to a downstream end of the second pipe.
 5. The exhaust systemof claim 1 wherein the diesel particulate filter includes a housinghaving an inlet channel and a brick mounted in the housing having afirst end and an opposed second end, with the brick selectivelymountable in the housing in a first orientation with the first endfacing the inlet channel and in a second orientation with the second endfacing the inlet channel.
 6. The exhaust system of claim 1 including acontroller, an upstream pressure sensor located adjacent to the firstpipe and operable to measure an upstream pressure in the exhaust gases,and a downstream pressure sensor located adjacent to the second pipe andoperable to measure a downstream pressure in the exhaust gases, with theupstream and downstream pressure sensors in communication with thecontroller.
 7. The exhaust system of claim 1 wherein the first mountingflange is removable from one of the first pipe and the second pipe andreinstallable on the other of the first pipe and the second pipe, andthe second mounting flange is removable from the other of the first pipeand the second pipe and reinstallable on the one of the first pipe andthe second pipe to thereby allow for reversal of the diesel particulatefilter in the exhaust system.
 8. The exhaust system of claim 7 includinga controller operable to detect at least one parameter correlating to anash buildup in the diesel particulate filter and operable to determine areversal or replacement of the diesel particulate filter is needed. 9.The exhaust system of claim 1 including a controller operable to detectat least one parameter correlating to an ash buildup in the dieselparticulate filter and operable to determine a reversal or replacementof the diesel particulate filter is needed.
 10. A method of monitoringand servicing a diesel particulate filter that may become loaded withash, in an exhaust system of a vehicle having a diesel engine, themethod comprising the steps of: (a) monitoring at least one parameterindicative of a buildup of the ash in the diesel particulate filter; (b)determining from the at least one parameter if action is required due tothe ash buildup in the diesel particulate filter; (c) indicating thatdiesel particulate filter servicing is needed when it is determined instep (b) that action is required; and (d) reversing a direction ofexhaust flow through a brick in the diesel particulate filter when step(c) indicates the servicing is needed and if the reversal is desirable.11. The method of claim 10 wherein step (a) is further defined by the atleast one parameter including at least vehicle mileage.
 12. The methodof claim 10 wherein step (a) is further defined by the at least oneparameter including at least detecting a difference in pressure betweenan upstream end and a downstream end of the diesel particulate filter.13. The method of claim 10 wherein step (d) is further defined byremoving the brick from a housing of the diesel particulate filter andreinstalling the brick in a reverse direction.
 14. The method of claim10 wherein step (d) is further defined by removing the dieselparticulate filter from the exhaust system, and reinstalling the dieselparticulate filter into the exhaust system in an opposite orientation.15. The method of claim 10 wherein step (d) is further defined by thereversal being desirable if the direction of exhaust flow through thebrick in the diesel particulate filter has not been previously reversed.16. The method of claim 10 including the step of: (e) replacing thediesel particulate filter in the exhaust system when step (c) indicatesthat servicing is needed and reversal of the direction of exhaust flowthrough the brick is not desirable.
 17. The method of claim 10 whereinstep (c) is further defined by the indication that servicing is neededincluding lighting an indicator light on the vehicle.
 18. A method ofregenerating and servicing a diesel particulate filter in an exhaustsystem of a vehicle having a diesel engine, the method comprising thesteps of: (a) operating the diesel engine and exhaust system in a normaloperating mode; (b) monitoring at least one soot parameter indicative ofsoot buildup in the diesel particulate filter while operating in thenormal operating mode; (c) monitoring at least one ash parameterindicative of a buildup of the ash in the diesel particulate filter; (d)determining from the at least one soot parameter when the dieselparticulate filter needs regenerating; (e) operating the vehicle in aregeneration mode, if it is determined in step (d) that the dieselparticulate filter needs regenerating; (f) determining from the at leastone ash parameter if action is required due to the ash buildup in thediesel particulate filter; and (g) reversing a direction of exhaust flowthrough a brick in the diesel particulate filter when step (f)determines that action is required.
 19. The method of claim 18 whereinstep (g) is further defined by removing the brick from a housing of thediesel particulate filter and reinstalling the brick in a reversedirection.
 20. The method of claim 18 wherein step (g) is furtherdefined by removing the diesel particulate filter from the exhaustsystem, and reinstalling the diesel particulate filter into the exhaustsystem in an opposite orientation.